In recent years, wireless networks take a form of an overlay network in which a plurality of wireless networks, e.g., a radio access network for high-speed data transmission, a broadband cellular network, and a local area network (LAN) are co-existed and thus their service areas overlap.
In such an overlay network environment, to provide a seamless service to a mobile terminal from an optimal network regardless of the location of the mobile terminal, it is necessary to provide a vertical handover technique that enables the mobile terminal to select an optimal one of the multiple networks and connect to the optimal network.